"To solve this problem you should reduce the MTU packet size on your router and or on your computer until the fragmentation stops. A simple test for MTU issues can be found here ( http://support.iprimus.com.au/static-pages/mtu-eyechart.html ), called the MTU Eyechart. The MTU Eyechart works by displaying a series of images of certain sizes, increasing down the page. If you get part way and some of the images stop loading, this should indicate what size packets are being dropped."

Keep lowering the size (1492) until it no longer says "Packet needs to be fragmented but DF set". Then begin increasing the packet size from this number in small increments until you find the largest size that does not fragment. Add 28 to that number (IP/ICMP headers) to get the optimal MTU setting. For example, if the largest packet size from ping tests is 1462, add 28 to 1462 to get a total of 1490 which is the optimal MTU setting. :

C:\Documents and Settings>ping yahoo.com -f -l 1492

Pinging yahoo.com [68.180.206.184] with 1492 bytes of data:

Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.